Beverage inspection machine



Sept. 9, 1947. I P. WEATHERS 2,427,319

BEVERAGE INSPECTION MACHINE Filed Jan. 12, 1945 2 Sheets-Sheet 1 Ava iv 500 WWW"! (4N) mf -wa of/ml l allaye rraezviy S pt.- 9, 1947.

P. WEATHERS B VEMGEL INS PECTION MACHINE Filed Jan. 12, 1945 2 Sheets-Shet 2 (lttorneg Patented Sept. 9, 1947 BEVERAGE INSPECTION MACHINE Paul Weathers, Upper Darby, Pa., assignor to Radio Corporation of America, a corporation of Delaware Application January 12, 1945, Serial No. 572,545

7 Claims.

This invention relates to the inspection of fluids in light-transmitting containers for the purpose of detecting the presence of foreign particles in the fluid. 'The invention has particular reference to an improved amplifier of signals generated in apparatus employed in such inspection.

In one practical inspection system for bottled beverages the bottle or light-transmitting container .and its vfluid contents are spun rapidly about the axis of the bottle. The rotary movement of the bottle is then suddenly stopped, but the fluid and any particles which it may contain continue to rotate. At this time a beam of light or other radiant energy is directed through the fluid to a photoelectric device or other appropriate radiant energy responsive mefis. Any rotating particle will affect the amount of light passing to the photoelectric device and thus generate signals which may be amplified and employed to actuate reject or indicating mechanisms.

In the system outlined, a large particle will obstruct more light than a small one and will, thereforageneratev a signal of greater amplitude than a small particle. For this reason it becomes necessary to provide suflicient amplification so that aparticle of the smallest size desired to be detected will be able to actuate the relays which, in turn, control the reject mechanism. High amplification, however, also amplifies signals due to noise, dust particles, vibration of the tubes and of the machine generally, .microphonics, etc.; and it therefore slows down the process of inspection and creates undesired rejections.

One of the objects of the invention is to provide improved bottle inspection apparatus which has substantially constant sensitivity over a given range of particle sizes and which is capable of distinguishing between particles of different sizes.

A further object is the provision of apparatus by the use of which bottled beverages may be inspected more quickly than heretofore and with a reduced numberof undesired rejections.

Another object is to provide an amplifier with optimum signal-to-noise ratio for apparatus of the type described. 7

A further object is the provision ofv an improved methodof inspecting beverages to detect particles of dilferentsizes.

.It was ,formerlyrecognized that the frequency of pulses generated in apparatus of .the type outlined depends upon the speed at which the fluid contents are rotated. The present invention, however, is based upon the fact that when other conditions affecting the same are constant the frequency of the generated pulsesis a function 2 of the size of the light intercepting particles. The smaller the particle, the higher is the frequency of the pulses.

The objects of the invention are achieved by so relating the degree of amplification to a band of pulse frequencies, corresponding to a range of particle sizes to be detected, that sensitivity is constant over that range. Furthermore, the amplification is abruptly reduced at frequencies in excess of a frequency corresponding to the smallest size of particle to be detected thereby rendering the apparatus insensitive to particles smallerthan those it is desired to detect.

In the accompanying drawing,

Figure 1 isa diagram illustrating the principle which forms the basis of the invention,

Figure 2 is a graph showing the frequency response of an amplifier according to the invention, and

Figure 3 is a schematic diagram of an amplifier for carryingthe invention into effect and of associated apparatus.

Fig. 4 is a partial plan view of apparatus suitable for spinning the contents of a bottle and for stopping the bottle while the contents thereof remain spinning in the path of an inspection beam.

Fig. 5 is a transverse section through the apparatus of Fig. 4 showing the mechanism for stopping the bottle at the inspection point.

In Fig. 1 particles of three different sizes are shown crossing a beam of light It and the wave forms of signals generated by the particles as they cross the beam are shown opposite each particle. When the particle is smaller in diameter than the beam, two pulses occur each time a particle crosses the beam; one when it enters, and one. when it leaves the beam. But when the particle is comparable in diameter to the width of the inspecting beam, the two pulses come together to form a continuous wave. It will be seen that the lope of the pulses caused by the smallest particle is comparatively steep and that this slope becomes more gradual as the size of the particle. increases. The frequency of the generated pulses depends upon the transit time of the whole of a particle through the beam. A small particle will traverse the beam in less time than a big one. When the velocity of the particles is constant the frequency of the generated pulses increases as the size of the particles causing them diminishes. Although the three wave forms of Fig. 1 are shown for convenience on equal time bases, it willbe apparent that the period of a pulse caused by a large particle will be greater than the period of a pulse caused by a smaller particle.

Fig. 2 is a frequency-response curve of an amplifier which may be used in beverage inspection apparatus of the character described and which makes use of the principles hereinbefore discussed. It was formerly the practice to make use of the accumulated charge caused by the particle crossing the light beam a number of times. Under this practice, pulses of comparatively low frequency (say from 8 to d cycles per second) were generated and the amplifier was tuned to peak in that range. See, for example, U. S. Patent No. 2,192,568, which issued on March 5, 1940, to Paul Weathers and which is assigned to the same assignee as the instant application. In recent commercial practice the bottles are spun at, say, 1700 revolutions per minute and signals of frequencies up to 200 and 300 cycles per second may be generated. The method described in U. S. Patent No. 2,268,098, which issued on December 30, 1944, to Paul Weathers and which is assigned to the same assignee as the instant application, may be used to bring the bottle contents uniformly up to the. desired speed without violent surface'disturbances of the liquid.

A described in Patent 2,268,098 and as shown in Figs. 4 and 5 of the instant application a turntable may be used to carry the containers to be inspected past an inspection point. The bottles indicated at H are carried by the turntable past the inspection point at which light is directed through the bottle onto the photocell 12 by means of an optical system 13. Since the table is moved continuously, the optical system is caused to swing with the bottle being inspected about a pivot coaxial with the turntable 10.

The turntable is driven by an appropriate gear 14 and the bottle is caused to spin or stop, as the case may be, by an appropriate pulley I5 coupled to the cup supporting the bottom of each bottle. As the turntable rotates in a clockwise direction in Fig. 4, the pulleys 15 connected to the successive bottles are brought in contact with the belt 16 which is carried on the pulleys 11, 18, and 19 and driven by the motor 80. This belt is driven at a speed depending upon the rate of inspection of the bottles and the speed of rotation of the contents desired at the inspection point. As the bottles come in contact with the belt just a little before reaching the point 8|, they are started in a spin and this spin continues to the point where the pulleys 15 connected to the bottles lose contact with the belt. During this time the entire bottle and supporting mechanism is brought up to a desired speed and is held there for a time of the order of one half a second to one second. This causes the outer portion of the contents to be brought up to the same speed as the bottle and at the same time causes a rather deep vortex at the surface due ,to the high speed of the periphery of the contents, while the central portion remains practically stationary. The bottle is permitted to spin freely for a moment until the pulley 75 reaches the brake shoe 86 supported by the bracket 85. This brake shoe 86 and the bracket 85 are substantially identical in construction to the brake shoe 9! and the bracket 90 shown in Fig. 5. When the pulley strikes the brake shoe 86, it is suddenly brought to a stop and'the bottle, of course, isalso stopped. This causes a braking eifect on the periphery of the contents but at the same time it causes the contents to stir around and the rapidly rotating peripheral portion mixes with the central portion causing the central portion of the contents to also start rotation so that at the end of the braking operation the entire contents of the bottle is rotating together, but at a somewhat slower speed than the peripheral portion was rotated previously. After leaving the brake, the bottles pas on to the point 83 where they are given a second spin in the same direction and at the same speed by contact with the belt, in order to bring the rotating contents up to the proper speed. After leaving the belt at this point, the contents pass on to the inspection point in alignment with the photocell 12 Where they are again stopped by the brake and 9| contacting with the pulley 15. At this point, in order to prevent vibration of the bottle, an additional brake shoe 92 and bracket 93 contacts with the upper member 94 holding the top of the bottle, thereby not only preventing rotation but also preventing oscillation of the bottle relative to the optical system.

The amplifier of the present invention is designed to have maximum gain for signals caused by particles of the smallest size which it is desired to detect. As previously mentioned, these signals may have frequencies of between 200 and 300 cycles per second. Signals of lower frequencies, caused by larger particles, are amplified to a less extent. The larger the particles, however, the greater is the amplitude of the signals they create; and by proper correlation, therefore, between the gain of the amplifier and the frequency of the signals which it amplifies, the amplifier may be made to have substantially constant output for signals caused by particles in a range of different sizes. As will be seen from a consideration of Fig. 2, the amplifier has a rising frequency-response characteristic up to a frequency corresponding to the smallest particle to be detected, and the relation between amplifier gain and frequency is substantially linear in this region. The signal-to-noise ratio is then optimum for that range of particle sizes.

The gain of the amplifier is abruptly reduced for signals whose frequency is in excess of that caused by the smallest particle to be detected. By this means, false rejections caused by particles smaller than it may be desired to detect, and by dust, noise, microphonics, transient disturbances, vibration and the like, are substantially reduced.

Fig. 3 is a circuit diagram of an amplifier according to the invention and of associated apparatus. Two phototubes l2 and I4, respectively, are connected between the control grid and cathode ol? a pentode amplifier l6 which is, in turn, connected in cascade with a second pentode amplifier la. The two amplifiers may be of RCA type 1620. The amplifier I8 is connected to a gas tube 20 which may be of RCA type 0A4-G and is designed when conducting to actuate a relay 22, which in turn controls reject mechanism.

In practice, the phototubes I2 and I4 may consist of two equal banks of tubes, the tubes of each bank being connected in parallel. Light from the inspecting beam H3 (Fig. 1) passes through the fluid contents of a bottle under inspection and is distributed between the two banks equally. In the absence of any particle, the output of one bank of phototubes is balanced against the equal output of the other bank. The phototubes I2 and M are coupled to the amplifier I6 by a capacitor 25 and a resistor 62. The amplifier I5 is coupled to the amplifier M by a capacitor 28 and resistors t4 and 58. The screen grid circuit of the amplifier 16 includes a capacitor 30 and a resiston 34-; similarly; .tl're screenr. grid circuit ,of: the amplifien l:8-:iincludes. a capacitor izland a: resise tor-362 The-- rising-characteristic curve-v ot Fig.2 issobtainedaby-ochoosingsuchvaluessfor' thesecae pacitors and resistorsthat the impedance. of each of the capacitors, at frequencies for-whichadiscriminationistdesired, is low in relation to that of the resistors with which each is associated.

A capacitor '38 -isconnectedbetween the amplifier 1-8. and the gas tube-12.0 the. charge on, this capacitor being employed to igniteg-the-gasetube 20. The desired high frequency, cut-off is obtained b-ythe insertiorr of an iron core inductor 4i] insseries with the signal-.circuit, thus forming a. single .section,. IQWrPfiSS filtenwith capacitor 38.

A double diode 42, shown in the lower portion of the circuit diagram, serves a dual purpose. This tube may be of RCA type 61-16. A time delay relay 44 i connected to one half of the double diode and is designed to delay operation of the inspection apparatus until the relay is closed. When power is applied to the amplifier, approximately ten seconds are required before the amplifier tube become sufliciently heated to function normally. The same period is required before the double diode will function, and the normal heating time required by this tube is used to delay closing of the relay 44. This will prevent operation of the inspecting apparatus until all tubes are properly heated, and also if the applied power, the amplifier fuses or the rectifier 46 should fail.

When the beverage inspection machine is stopped, there will be a number of bottles in it which have not been spun sufficiently for adequate inspection. The other half of the double diode, together with apparatus now to be described, constitutes a timing circuit which is used to reject all of such bottles for a short period after the machine is started again.

When the switch 48 is open, alternating current from a source indicated at 6B is rectified and places a charge upon a capacitor 5|] in series with a resistor 52. When the switch 48 is closed, the capacitor discharges and causes a neon tube 54, which may be of RCA type 991, to conduct. Current. therefore, flows through resistors 56 and 58 to ground and applies a negative potential to the control grid of the second amplifier l8. This, in turn, cause the gas tube 20 to conduct and actuates the reject relay 22 just as though a particle had crossed the inspecting 'beam and a signal had been applied from the phototubes l2 and !4 through the first amplifier IS. The components of the timing circuit just described are so chosen as to create a delay of, say, three to six second after the machine has been restarted, and this will ordinarily be sufficient to reject all bottles drawn into the machine from the previous operation.

There has thus been described an amplifier for beverage inspection apparatus which has substantially constant sensitivity for a given range of particle sizes to be detected and which is designed to give no effective response for particles below a given size. This result is secured by correlating the gain of the amplifier with the frequency of signals generated in the apparatus, that frequency corresponding to the size of the actuating particle when other factors affecting the same are equal. By the use of the method described. the signal-to-noise ratio and the speed of inspection may be increased, and the number of rejections reduced.

I claim as my invention:

1:.:In the,.:. method; of inspecting fluid. in a translucent container: to,-.-detect:; the presence of foreign; partiolesehaving; a. certain'range, of sizes in?-the.;.fllllid;' said method-including. moving; the

5 fiuidithrouglrratb'eamcofi'radiant; ener y While. the. container is stationarya relative to, the beam and detecting: electric; pulses; .causediby; movement. of the particles through the beam, the step. ofselectively amplifying-pulse of; different frequencies c aused by movementi of particles within said range offlsizes throughthe beam.

2'; The method: of detecting-the presence of foreign particles-.havinga" certain range, of sizes in fluid in a=- translucent container, which consists in-directir1=gabeam-ot light to a photoelectric=- device -throug-l-rsaid fluid 1 while the fluid is rotating and the container is stationary, whereby to generate in said device pulses of different frequencies corresponding to different sizes within said range of sizes of said particles, amplifying said pulses, and so relating the degree of said amplification to the frequency of said pulses that the amplitude of said amplified pulses is substantially constant for said given range of particle sizes.

3. The method of detecting the presence of foreign particles having a certain range of sizes in fluid in a translucent container, which consists in directing a beam of light to a photoelectric device through said fluid While the fluid is rotaing and the container is stationary, whereby to generate in said device pulses of different frequencies corresponding to different sizes within said range of sizes of said particles, amplifying said pulses, and maintaining a substantially linear relation between the degree of said amplification and the frequency of said pulses such that the amplitude of said amplified pulses is substantially constant throughout said range.

4. The method of detecting the presence of foreign particles in fluid in a translucent container, which consists in moving the fluid through a beam of radiant energ while the container is held stationary relative to the beam, amplifying pulses 45 .of current caused by the movement of said particles through said beam, said pulses being of different frequencies corresponding to different sizes of particles within a given range, amplifying said pulses, maintaining a linear relation be- 50 tween the degree of said amplification and the frequency of current pulses corresponding to sizes of particles within said range so that the amplitude of said amplified pulses is substantially :constant throughout said range, and attenuating pulses of current of frequencies in excess of a frequency corresponding to the smallest size of particle in said range.

5. In apparatus for detecting the presence of foreign particles in fluid in a translucent con- 60 tainer, the combination with means for moving said fluid through a beam of radiant energy while the container is held stationary relative to the beam whereby to generate pulses of current of different frequencies caused by movement of 5 particles of different sizes through said beam, of an amplifier for said pulses having a rising frequency-response characteristic covering a band of frequencies corresponding to the sizes of particles to be detected.

6. In apparatus for detecting the presence of foreign particles in fluid in a translucent container, the combination with means for moving said fluid through a beam of radiant energy while the container is held stationary relative to the beam whereby to generate pulses of current 7 of different frequencies caused by movement of particles of different sizes through said beam, of an amplifier for said pulses having a, substantially linear, rising frequency-response characteristic covering a band of frequencies corresponding to the sizes of particles to be detected.

7. In apparatus for detecting the presence of foreign particles in fluid in a translucent container, the combination with means for moving said fluid through a beam of radiant energy while the container is held' stationary relative to the beam whereby to generate pulses of current of different frequencies caused by movement of particles of different sizes through said beam, of an amplifier for said pulses having a rising frequency-response characteristic covering a band REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Stout Oct. 11, 1938 Number 

